FR2802293A1 - APPARATUS AND METHOD FOR SEPARATION BY CRYOGENIC DISTILLATION - Google Patents

Abstract

The invention relates to a separation device which does not produce ultra-pure products. At least one distillation column which has a diameter of at least 4 m and/or is configured for operation at a pressure above 4.5 bar, consists of non-oxidizing steel or steel containing 9 to 10 % by weight nickel. The separation device can be an air separation device.

Description

The present invention relates to an apparatus and method for separation by cryogenic distillation.

Cryogenic distillation is mainly carried out in aluminum or steel columns, in particular in steel containing nickel or chromium nickel (Tieftemperaturtechnik, pages 480 and 482.) It is also known from J03204582 to construct separation columns for stainless steel air to avoid contamination of ultra-pure products.

It is necessary to produce ever greater quantities of air fluid such as oxygen and projects of oxygen at high pressure are envisaged in the near future.

In the case of aluminum, the thicknesses of the columns become very large, which imposes extremely penalizing manufacturing and control constraints. For a column of 6 meters in diameter, under an operating pressure of 15 bars, with aluminum the thickness of the column ferrule is approximately 66mm. By using stainless steel, it becomes possible to reduce this thickness to 40mm.

The pressures discussed in this document are absolute pressures.

According to an object of the invention, there is provided a cryogenic distillation apparatus comprising at least two columns including at least one first column which is that or one of those designed to operate at the highest pressure has a ferrule stainless steel or steel containing between 8 and 10% nickel, means for sending a mixture to be separated to one of the columns, possibly the first column, and means for withdrawing fluids, enriched in a component of the mixture, of a columns characterized in that the first column is designed to withstand pressures greater than 4.5 bar and / or in that the diameter of the column is greater than 4 meters.

Preferably the column (s) designed to operate at the lowest pressure contains less than 80 theoretical plates.

According to another object of the invention, there is provided a cryogenic distillation apparatus comprising a single column having a ferrule made of stainless steel or steel containing between 8 and 10% of nickel, means for sending a mixture to the column and means for withdrawing fluids enriched in a component of the column mixture characterized in that the column is designed to withstand pressures greater than 4.5 bar and / or in that the diameter of the column is greater than 4 meters.

Preferably the simple column contains less than 80 theoretical plates.

According to other optional aspects of the apparatus mentioned above - the column designed to operate at the lowest pressure contains less than 60 theoretical plates, possibly less than 50 theoretical plates or less than 40 theoretical plates.

- the device comprises at least one other column with an aluminum or stainless steel or steel ferrule containing between 8 and 10% of nickel. - the diameter of one of the columns having a stainless steel or steel ferrule containing between 8 and 10% of nickel is greater than 5 m, possibly 6 m.

According to another aspect of the invention, there is provided a cryogenic distillation process in a separation apparatus comprising at least one column of which at least the column operating at the highest pressure is made of stainless steel or of steel containing between 8 and 10% nickel in which a mixture is sent to one of the columns where it separates into fluids enriched with more volatile and less volatile components characterized in that the column (s) made of stainless steel or of steel containing between 8 and 10% of nickel operates at at least 4.5 bara and / or has a diameter of at least 4 meters and / or in that the separation apparatus produces as final product at least one fluid not comprising more than 98 mol.% Of its main component. Thus liquids and gases containing more than 98 mol.% Of their main component can be produced but there is at least one impure product (containing less than 98 mol.% Of its main component).

According to other optional aspects of the invention - the separation apparatus is an air separation apparatus which produces at least as gaseous oxygen-rich end products fluids comprising not more than 98 mol .-% oxygen , possibly 95mol .-% oxygen, possibly 85mol-% oxygen. Liquids richer in oxygen, for example containing at least 99 mol% of oxygen, can be produced simultaneously.

the separation apparatus is an air separation apparatus which produces as final oxygen-rich gaseous products only fluids comprising not more than 98 mol .-% oxygen, possibly 95mol .-% oxygen, possibly 85mol-% oxygen. Liquids richer in oxygen, for example containing at least 99 mol% of oxygen, can be produced simultaneously.

- The separation device comprises a high pressure column thermally connected with at least one low pressure column and possibly a column operating at intermediate pressure between the high and low pressures.

- The separation device is an air separation device which produces at least as gaseous nitrogen-rich end products fluids comprising more than 1 ppm of oxygen, possibly 5 ppm of oxygen, optionally 10 ppm of oxygen. Liquids richer in nitrogen than this gaseous product, for example containing less than 1 ppm of oxygen can be produced simultaneously.

the separation apparatus is an air separation apparatus which produces as gaseous nitrogen-rich end products only fluids comprising more than 1 ppm of oxygen, possibly 5 ppm of oxygen, possibly 10 ppm of oxygen. Liquids richer in nitrogen than this gaseous product, for example containing less than 1 ppm of oxygen can be produced simultaneously. the process makes it possible to separate purified air or a mixture comprising at least 1% of nitrogen and / or at least 1% of carbon monoxide and / or at least 1% of hydrogen and / or at least 1 lo of hydrocarbons.

- the column (s) made of stainless steel or steel containing between 8 and 10% of nickel is (are) the high, intermediate or low pressure column of a double column or triple column or the mixing column of an air separation device.

- the column or at least one of the stainless steel or steel columns containing between 8 and 10% of nickel is a low pressure column or a mixing column of a double or triple column and the device produces gaseous oxygen having a maximum purity of 90mo1 .-%, possibly 85 mol% of oxygen withdrawn from the low pressure column or the mixing column.

- The column or at least one of the columns in stainless steel or containing between 8 and 10% of nickel is supplied with purified air and / or a mixture enriched in nitrogen and / or oxygen and / or argon.

the column or at least one of the columns made of stainless steel or containing between 8 and 10% of nickel operates at a pressure above 7.5 bars, optionally above 10 bars, optionally above 12 bars, possibly above 14 bars.

The stainless steel is of the 4307 or 4306 or 304L type and the steel containing between 8 and 10% of nickel preferably contains 9% of nickel (type A353). Typically for a stainless steel column ferrule, for an operating pressure of 5 bara and a diameter of 5m, following the ASME code, a thickness of the order of 12 mm in stainless steel is necessary, for an operating pressure of 12 bara and a diameter of 5m, with the same code a thickness of around 30 mm in stainless steel is necessary and for an operating pressure of 15 bara and a diameter of 5m a thickness of around 40 mm stainless steel is required.

An example of this kind of process will now be described.

In an air distillation apparatus, according to the invention, the air is separated in a double column comprising a high pressure column operating at 15 bava and a low pressure column operating at 5 bara. Each column includes a stainless steel ferrule with a diameter of around 5m. The ferrule of the high pressure column has a thickness of 40mm and the ferrule of the low pressure column has a thickness of 12mm. The low pressure column contains 40 theoretical plates in the form of structured packings.

The columns contain packings structured in aluminum or stainless steel or in steel containing between 8 and 10% of nickel or copper.

The or certain pipes connecting the columns, for example for transferring the rich liquid and the lean liquid from the high pressure column to the low pressure column are made of stainless steel or of steel containing between 8 and 10% of nickel.

The device produces a flow of gaseous oxygen comprising at most 98 mol% of oxygen in the bottom of the low pressure column. No gas or liquid purer in oxygen is produced by the device.

The apparatus also produces, as the purest nitrogen gas, a gas flow comprising 98 mol% of nitrogen, or preferably 95 mol. lo of nitrogen. Alternatively, in the double column described above, the high pressure column can for example have a stainless steel or steel ferrule containing between 8 and 10% of nickel and the low pressure column can have an aluminum ferrule.

The two columns can be placed side by side as described in French patent application S4531 (Francine - please replace with the publication number) and not one above the other.

 Obviously the distillation columns operating below 4.5 bar and / or having a diameter below 5m can have ferrules made of stainless steel or containing 9% of nickel thinner than with aluminum and can produce end products rich in oxygen, nitrogen or argon.

In a triple column as described in EP-A-0538118 to Ha, there is a high pressure column, a column operating at a pressure between high and low pressures and a low pressure column. All these columns can operate at a pressure above 4.5 bar with a diameter greater than 5m.

If it is necessary to choose which of the columns will have a ferrule made of stainless steel or of steel containing between 8 and 10% of nickel, preferably containing 9% of nickel, we will favor the high pressure and medium pressure columns, possibly by placing these columns at side of the low pressure column. Optionally just the high pressure column or the medium pressure column will have a stainless steel or steel ferrule containing between 8 and 10% nickel.

Similarly, in an installation comprising a double column and a mixing column operating at a much higher pressure than the high pressure column of the double column, the mixing column will be made of stainless steel or of steel containing between 8 and 10% of preferably nickel containing 9% nickel and the other columns could be of the same type of steel.

Claims (1)

<U> Claims </U> 1. Cryogenic distillation apparatus comprising at least two columns including at least one first column which is that or one of those designed to operate at the highest pressure has a ferrule made of stainless steel or steel containing between 8 and 10% of nickel, means for sending a mixture to be separated to one of the columns, possibly the first column, and means for withdrawing fluids, enriched in a component of the mixture, from one of the columns characterized in that the first column is designed to withstand pressures greater than 4.5 bar and / or in that the diameter of the column is greater than 4 meters. 2. Apparatus according to claim 1 wherein the column (s) designed to operate at the lowest pressure contains less than 80 theoretical plates. 3. Cryogenic distillation apparatus comprising a single column having a stainless steel or steel ferrule containing between 8 and 10% nickel, means for sending a mixture to the column and means for withdrawing fluids enriched in a component of the mixture of the column characterized in that the column is designed to withstand pressures greater than 4.5 bar and / or in that the diameter of the column is greater than 4 meters. 4. Apparatus according to claim 3 wherein the column contains less than 80 theoretical plates. 5. Apparatus according to one of the preceding claims wherein the column designed to operate at the lowest pressure contains less than 60 theoretical plates. 6. Apparatus according to claim 5 wherein the column designed to operate at the lowest pressure contains less than 50 theoretical plates. 7. Apparatus according to claim 6 wherein the column designed to operate at the lowest pressure contains less than 40 theoretical plates. 8. Apparatus according to claim 1 comprising at least one other column with an aluminum ferrule or stainless steel or steel containing between 8 and 10% nickel. 9. Apparatus according to one of the preceding claims in which the diameter of a column having a ferrule made of stainless steel or steel containing between 8 and 10% of nickel is greater than 5 m, possibly 6 m. 10. A method of cryogenic distillation in a separation apparatus comprising at least one column, at least the column of which operates at the highest pressure, is made of stainless steel or of steel containing between 8 and 10% nickel, in which a mixture is sent to one of the columns where it separates into fluids enriched in more volatile and less volatile components characterized in that the column (s) made of stainless steel or steel containing between 8 and 10% of nickel operates at least 4 , 5 bara and / or has a diameter of at least 4 meters and / or in that the separation apparatus produces as final product at least one fluid comprising not more than 98mol.% Of its main component. 11. The method of claim 10 wherein the separation apparatus is an air separation apparatus which produces at least as gaseous end products rich in oxygen from fluids comprising not more than 98 mol .-% oxygen, optionally 95mol .-% oxygen, possibly 85mol-% oxygen. 12. The method of claim 11 wherein the separation apparatus is an air separation apparatus which produces as end products gaseous oxygen-rich only fluids comprising not more than 98 mol .-% oxygen, optionally 95mo1 .-% oxygen, possibly 85mol-% oxygen. 13. Method according to one of claims 10 to 12 wherein the separation apparatus comprises a high pressure column thermally connected with at least one low pressure column and optionally a column operating at intermediate pressure between high and low pressures. 14. The method of claim 10 to 13 wherein the separation apparatus is an air separation apparatus which produces at least as gaseous nitrogen-rich end products fluids comprising more than 1 ppm oxygen, optionally 5 ppm d oxygen, possibly 10 ppm oxygen. 15. The method of claim 14 wherein the separation apparatus is an air separation apparatus which produces as gaseous nitrogen-rich end products only fluids comprising more than 1 ppm of oxygen, optionally 5 ppm of oxygen , possibly 10 ppm oxygen. 16. Process for the cryogenic distillation of purified air or of a mixture comprising at least 1% of nitrogen and / or at least 1% of carbon monoxide and / or at least 1% of hydrogen and / or at least 1 % of hydrocarbons according to one of claims 10 to 15. 17. Method according to claim 16 in which the column (s) made of stainless steel or steel containing between 8 and 10% of nickel is (are) the high, intermediate or low pressure column of a double column or triple column or the mixing column of an air separation device. 18. The method of claim 17 wherein the stainless steel or steel column containing between 8 and 10% nickel is a low pressure column or a mixing column of a double or triple column and the apparatus produces oxygen gas having a maximum purity of 90mo1 .-%, possibly 85 mol% of oxygen withdrawn in gaseous form and / or in liquid form, and then vaporized, from the low pressure column or the mixing column. 19. Method according to one of claims 16 to 18 in which the column made of stainless steel or containing between 8 and 10% of nickel is supplied with purified air and / or a mixture enriched in nitrogen and / or oxygen and / or argon . 20. Method according to one of claims 10 to 19 wherein the column made of stainless steel or containing between 8 and 10% of nickel operates at a pressure above 7.5 bars, optionally above 10 bars, optionally above above 12 bars, possibly above 14 bars.